(1) Field of the Invention
The present invention relates to a corrosion coupon rack of the type used to support coupons within a liquid conduit to evaluate corrosion, and in particular to a rack including coupon holders that can be rapidly and easily removed and reinserted into the rack.
(2) Description of the Prior Art
Corrosion coupon racks provide a convenient means of monitoring the progress of corrosion in systems such as boilers, condensate lines, open recirculating cooling water, closed circulating hot or chilled water systems, etc. By monitoring the corrosion rate of inexpensive coupons, information is obtained that can avoid damage to expensive piping systems. A corrosion rack creates a side stream off the main system in which corrosion test coupons can be exposed to system water under controlled and reproducible conditions.
Corrosion racks used in conjunction with high temperature and high pressure installations are constructed of black iron pipe, while corrosion racks used in low temperature systems are normally constructed of PVC pipe, e.g., one inch pipe with corresponding T-joints, elbows, valves, etc. The rack is normally arrayed in a zig-zag fashion and may include one or more, e.g., up to six, coupon holders that are normally positioned at the outer ends of T-connectors so that the coupon held by the coupon holder extends into a horizontal pipe on the opposite side of the T-connector. Water is then conveyed though the vertical section of the T-connector and though the horizontal pipe, flowing over the coupon. Generally, the coupons, which are conventionally thin bars of metal, e.g., mild carbon steel or copper, are removed from the pipe for examination anywhere from monthly to yearly, e.g., every 90 days, depending on the corrosion conditions. The corrosion coupons are visually examined, weighed, and evaluated for corrosion rate, and pitting severity.
Conventional coupon holders are comprised of a shaft with a distal end adapted to detachably support a coupon, and a proximal end attachable to a threaded cap that is screwed onto the rack to position the shaft and an attached coupon into a horizontal pipe. Many caps require a tool for removal, although some coupon racks purport to use caps that can be unscrewed by hand without the use of a tool. In any event, the necessity of unscrewing coupon holders to remove or replace coupons is laborious and time consuming, particularly if a large number of coupon holders are involved. Therefore, there is a need for an improved corrosion coupon holder, and a corrosion coupon rack that includes one or more of such holders, that can be quickly and easily removed and replaced, while securely holding the coupon in place without leakage when in position.